This invention relates to an optical part used for an optical communication system, and particularly to an optical switch suitable for switching or intercepting an optical path.
There are two types of optical switches. The first type is a waveguide type optical switch using a quartz optical waveguide or a lithium niobate crystal optical waveguide. The second type is a mechanical optical switch that mechanically moves an optical fiber or a prism.
An optical switch of the first type performs switching by changing the refractive index of a part of an optical waveguide. To change the refractive index of a part of the optical waveguide, a current is caused to flow through a thin film electric heater installed on the optical waveguide, or a voltage is applied to an electrode using an electro-optical effect. The optical switch of the first type has the advantage of being reliable because it has no moving part. However, the optical switch of the first type has a problem that it is generally expensive and has large loss. Therefore, most of the optical switches that are actually used are those of the second type.
As an optical switch of the second type, there is known an optical switch having an input optical fiber, a flat optical waveguide plate arranged at a position facing an output end surface on the input optical fiber, plural output optical fibers fixed on this flat optical waveguide plate, and a moving unit for relatively moving the positions of the input optical fiber and the flat optical waveguide plate. This optical switch switches an optical path by mechanically changing the relative positions of the input optical fiber and the flat optical waveguide plate. Such an optical switch is disclosed, for example, in JP-A-2001-174725. The optical switch of the second type is less expensive and has smaller loss than the optical switch of the first type. However, since the optical switch of the second type has a moving part, its reliability is low.
As optical communication networks have been recently set up in various areas of cities, an optical switch of lower price and higher reliability is required in order to realize a function of flexibly controlling signal paths of the networks.